spectrum- for sunlight and other white light, the spread of colors seen when the light is passed through a prism or diffraction grating. In general, the spread of radiation by frequency, so that each frequency appears at a different position.
The spectrum of colors in white light (in order) are: red, orange, yellow, green, blue, and violet.
They can be seen and separated by use of a prism (as seen below)
A prism separating white light
white light- light, such as sunlight, that is a combination of all the colors. Under white light, white objects appear white and colored objects appear in their individual colors.
This means that white is not a color itself, and instead it is a combination of all of the colors of light.
In addition to white, this also means that black is not a color, but only an absence of light.
Ch. 28 Section 2- Color by Reflection The colors of objects that we see everyday depends on the way that they reflect light that is shine upon them.
This rose absorbs blue and green, and reflects red
Keep in mind that electrons can be forced into larger orbits by vibrations of electromagnetic waves, and therefore send out their own energy waves in all directions.
All materials have their own natural frequencies for absorbing and emitting radiation.
When the electrons reach a material where amplitudes of oscillation are large, the light is then absorbed.
However, above and below the resonant frequency, the electrons (light) is reemitted.
In transparent objects, the reemitted light passes through
In solid (or opaque) objects, the light goes back to the medium where it came from (reflection)
White objects reflect all colors, while black absorbs all colors.
For objects that reflect a cerain color, in this case, some most colors are absorbed, and one color is reflected (the one you see)
However, most objects do not reflect only one frequency, but instead several.
Yellow can be made by absorbing blue and violet, and reflecting red, green, and yellow.
It is crucial to remember that colors can be changed by the illuminating light being used.
In candle light, something may appear more yellow, while under fluorescent light, it may appear more blueish.
Ch. 28 Section 3- Color by Transmission
pigment- a material that selectively absorbs colored light.
An object with a certain color pigment will absorb all other colors except it's own pigment, which it then transmits.
For example, in glass of certain colors, only the color of the glass is transmitted, and all other colors are absorbed, therefore only letting through some of the light.
This happens because the light from the other frequencies are reemitted from atom to atom.
An example of transmission through red glass
Ch. 28 Section 4- Sunlight
The sun
-The sun gives off white light, which is a combination of all colors of light.
-Although we might believe at first that the brightnesses of each color are even, we are mistaken.
-In actuality, the lowest frequencies of light (red and orange) are not nearly as bright as yellow and green.
-Because of this, yellow-green is actually the brightest part of sunlight (of which we are most sensitive to)
-In addition to reds and oranges, the opposite end made up of blue and violet is also not as bright.
-All of this is easily seen through a distribution of brightness verses frequencies in a radiation curve of sunlight.
-This can be seen on page 426 of the text book.
Ch. 28 Section 5- Mixing Colored Light
additive primary colors- red, blue and green light. These colors when added together produce white light.
This means that any color can be made with these three colors by adjusting the brightness of each one on the screen.
The primary colors always produce white light
Televisions are made this way in order to produce any color on the screen. By combining red, blue, and green very small lights and differing brightness, an image can be produced.
Ch. 28 Section 6- Complementary Colors
When three additive primary colors of light are mixed, they produce white.
However, when only two out of the three are mixed, they produce complementary colors.
red + green = yellow
red + blue = magenta
blue + green = cyan
When two of these new colors add together to make white, then they are described as complementary colors.
This means that every color also has a complementary color that produces white.
Also, if you subtract a color from white light, this results in that color's complementary.
yellow + blue = white
magenta + green = white
cyan + red = white
Ch. 28 Section 7- Mixing Colored Pigments
Paint pigments
subtractive primary colors- the colors of magenta, yellow and cyan. These are the three colors mose useful in color mixing by subtraction.
Although a combination of these colors produce white in light, in pigments, they instead create different colors.
This is because they instead absorb a lot of colors and only reflect their respective "pigment" color or mixtures of colors.
As an example: Blue paint reflects blue light, but also violet and green. It also absorbs blue and violet light. However, when it is mixed with yellow paint, it reflects green light and absorbs all other colors.
This concludes that mixing color with light is additive, and mixing with colors is subtractive.
Ch. 28 Section 8- Why the Sky is Blue
scatter- to absorb sound or light and reemit it in all directions
-First of all, it is important to remember that atoms and molecules reemit light waves that shine on them, and particles do the same.
-Because the particles are so tiny, the nitrogen and oxygen molecules as well as particles reemit light and is scattered when sun is shined upon them.
The little ultraviolet light that passes through the upper atmosphere and to the lower is then scattered by the particles in the air.
The high frequency colors (violet, blue) are scattered most, and lower frequencies are scattered the least.
However, the color of the sky also depends on the amount of dust particles which scatters lower frequencies more.
Also, the higher in the sky, the less molecules, and therefore darker sky
When there are no molecules (space) the sky is black
Clouds are made of microscopic water droplets (all different sizes) and therefore result in different frequencies of scattered light.
Low frequencies = large droplets
High frequencies = small droplets
They are bright because the small droplets vibrate together, which scatters more energy then if they had vibrated separately.
Blue Sky
Ch. 28 Section 9- Why Sunsets are Red
Sunset
Air is made up of nitrogen and oxygen molecules; these molecules most easily transmit lower frequencies of light.
Therefore, reds, oranges, and yellows pass through thick atmospheres (which occur during sunset and sunrise) while the others are scattered.
When the sun is most horizontal to the horizon, the light that must reach the earth must pass through the most amount of atmosphere, only allowing reds through the air. This is also why sunsets are always these colors!
Ch. 28 Section 10- Why Water is Greenish Blue Water is clear to all of the visible frequencies of light, not blue.
This is because water molecules abosorb infrared light waves that resonate to the frequencies of the infrared waves.
This energy from the infrared waves are then formed into kinetic eneregy of the water molecules, and then causes a gradual absorption of red light.
This process leaves the complementary color of red, cyan, which happens to be a greenish blue color.
This shows how any color of anything is depended on what colors are reflected by molecules, and also which are absorbed.
Greenish blue ocean
Ch. 28 Section 11- The Atomic Color Code - Atomic Spectra All elements have their own unique color when they emit light.
They are most easily seen and analyized when in their gaseous state.
This is because the atoms are far enough apart to emit their true colors.
spectroscope- an instrument used to separate the light from a hot gas or other light source into its constituent frequencies.
By using a thin slit, several lenses, and a prism, one can separate the gaseous light into separate frequencies.
They appear as a series of lines indicating the basis of the entire color of the element.
An example of a spectroscope line spectra
line spectrum- pattern of distinct lines of color, corresponding to particular wavelengths, that are seen in a spectroscope when a hot gas is viewed.
Sections:
Ch. 28 Section 1-The Color Spectrum
Ch. 28 Section 2- Color by Reflection
The colors of objects that we see everyday depends on the way that they reflect light that is shine upon them.
Keep in mind that electrons can be forced into larger orbits by vibrations of electromagnetic waves, and therefore send out their own energy waves in all directions.
Ch. 28 Section 3- Color by Transmission
-Although we might believe at first that the brightnesses of each color are even, we are mistaken.
Ch. 28 Section 5- Mixing Colored Light
Ch. 28 Section 6- Complementary Colors
Ch. 28 Section 7- Mixing Colored Pigments
Ch. 28 Section 8- Why the Sky is Blue
- scatter- to absorb sound or light and reemit it in all directions
-First of all, it is important to remember that atoms and molecules reemit light waves that shine on them, and particles do the same.-Because the particles are so tiny, the nitrogen and oxygen molecules as well as particles reemit light and is scattered when sun is shined upon them.
Ch. 28 Section 9- Why Sunsets are Red
Therefore, reds, oranges, and yellows pass through thick atmospheres (which occur during sunset and sunrise) while the others are scattered.
Ch. 28 Section 10- Why Water is Greenish Blue
Water is clear to all of the visible frequencies of light, not blue.
This is because water molecules abosorb infrared light waves that resonate to the frequencies of the infrared waves.
This energy from the infrared waves are then formed into kinetic eneregy of the water molecules, and then causes a gradual absorption of red light.
Ch. 28 Section 11- The Atomic Color Code - Atomic Spectra
All elements have their own unique color when they emit light.
They are most easily seen and analyized when in their gaseous state.
This is because the atoms are far enough apart to emit their true colors.
Sources